1. Field of the Invention
The present invention generally relates to mechanisms that are configured to produce a predictable output force in response to a linear input displacement. More particularly, this invention relates to a compliant mechanism that is capable of producing a substantially constant output force in response to a linear input displacement. Applications for such a compliant mechanism are diverse, and include such devices as electrical connectors in which a constant resistance force is desired during the connection procedure and throughout the life of the connector.
2. Description of the Prior Art
The use of springs as energy absorbers in mechanisms has a wide range of industrial applications, in that springs are capable of generating a predictable output force in response to a linear input displacement or deflection. However, there are many applications that would benefit significantly if the output force remained constant regardless of the amount of input deflection. Such applications include those in which a constant resistance force in response to a deflection is desired in order to prevent over-stressing and damage to components and structures.
Exact constant force mechanisms have been developed by Jenuwine and Midha using synthesis techniques, as disclosed in "Design of an Exact Constant Force Generating Mechanism," Proceedings of the 1st National Applied Mechanisms & Robotics Conference, Vol. II, Cincinnati, Ohio, pp. 10B-4-1-10B-4-5(1989); and "Synthesis of Single-Input and Multiple-Output Port Mechanisms with Springs for Specified Energy Absorption", Journal of Mechanical Design, Trans. ASME, Vol. 116, No. 3 (September 1994), pp. 937-943. These mechanisms employ two perpendicular linear springs acting on a rigid-body topology to obtain a constant force output, and illustrate the potential of a device that is capable of producing a substantially constant output force in response to a linear input displacement.
A notable application is electrical connectors, whose manufacturing tolerances are often of concern due to their significant effect on the assembly force required to make a complete connection. Automated assembly often entails the use of a constant assembly force. If the force exerted is too low relative to the force required to connect a particular assembly, a weak or incomplete connection may result due to insufficient travel of the connector. In contrast, if the assembly force is excessive so as to cause excessive travel of the connector, fracture or plastic deformation may result. In contrast, if the force required to make the connection were known and constant, the assembly force could be appropriately set to repeatably achieve the travel required to make a reliable connection.
Thus, it would be desirable to provide a relatively uncomplicated mechanism with which a predictable output force, and preferably a substantially constant output force, is produced in response to a linear input displacement to the mechanism. Such a mechanism would preferably be adaptable to various practical applications in which a constant resistance force in response to a deflection is desired, so as to prevent over-stressing of the components of the mechanism or the components being physically engaged by the mechanism.
In addition, such a mechanism should be capable of being manufactured with conventional materials and processing methods so as to yield a relatively light weight and inexpensive device. Moreover, such a mechanism should be scalable for applications as small as micro-electro-mechanical devices and as large as construction equipment.